EFFECTS OF TRANSIENT CEREBRAL-ISCHEMIA ON HSP40 MESSENGER-RNA LEVELS IN RAT-BRAIN

Rats were subjected to transient cerebral ischemia by four-vessel occl usion of 30 min duration, followed by 2, 4, 8 or 24 h of recovery. Tot al RNA was isolated from the cerebral cortex and hippocampus, and reve rse transcribed into cDNA. Hsp40 mRNA levels of samples were evaluated by quantitative PCR. Transient cerebral ischemia caused a marked incr ease in hsp40 mRNA levels to about 250% and 500% of control in the cor tex and hippocampus respectively. Since hsp40 exerts a critical regula tory function in the HSC70/HSP70 ATPase cycle, an ischemia-induced ris e of hsp40 mRNA levels could mark the onset of the recovery process af ter transient ischemia. On the other hand, the inhibitory action of hs p40 on P58 (a protein that activates protein synthesis by blocking the interferon-induced double-stranded RNA-activated protein kinase PKR) implies that the rise in hsp40 expression may equally well contribute to the post-ischemic suppression of protein synthesis. (C) 1998 Elsevi er Science B.V.